1. Field of the Invention
This invention relates to vehicular electronic equipment which receives control information from outside the vehicle for controlling electrical/mechanical vehicular accessories, and more particularly, receives the control information via an antenna which is located on the lower portion of the door window.
2. Description of the Prior Art
Based upon recent advances in wireless communications, wireless transmission apparatus have become miniaturized and more economical, leading to the common use of such equipment in vehicular apparatus. Such apparatus are also exhibiting increasing variety. Many of them are operated according to received signals through wireless means from outside the vehicle. For example, there are not only radio and television broadcasting receivers that operate according to signals received from outside the vehicle, there are also keyless entry systems like that disclosed in Japanese Patent Application Laid-Open No. 60-159268, which discloses a control means for door lock/unlock control equipment from the outside of the vehicle by wireless equipment. Also, for receiving various kinds of information for each part, there is a tendency to provide several antennas (FM, AM, TV, keyless entry antennas). For example, as in Japanese Utility Model Application Laid-Open No. 61-197714, there are antennas for radio and television (but not for keyless entry systems) placed on back door windows. In these systems, because of differences in transmitted signal frequencies of information sources, antennas must be of a length to match the frequency waveform of the information source, posing difficulties because of limited space in the vehicle. That is, because there are antennas for radio, television, wireless telephone, and various other wireless transmission systems, various portions of the vehicle, such as the windshield, rear window, etc., are occupied with antennas; it is thus not desirable to attach an additional antenna that extends outside the vehicle for the purpose of a keyless entry system controlling a door lock/unlock operation. For this reason, loop antennas are often attached to the side mirrors for this purpose.
Attaching a keyless entry system antenna to the front or rear window is difficult and also reduces visibility. However, it is also undesirable to locate the antenna at a distance from the control apparatus of the vehicular accessory device.